Removal of fuel from a fuel tank of a vehicle operating at extreme attitudes presents unique challenges not present in typical automotive applications. Fuel injection systems operate with a nearly constant flow of fuel through a, typically, electric fuel pump at flow rates well in excess of the maximum engine fuel demand. These high fuel rates greatly increase the probability that air will be drawn into the pump, and thus the fuel rail, and this can cause erratic engine performance ranging from misfire to engine shut off and can in turn cause damage to the engine. Current designs to overcome this problem involve the use of two or more pickups placed on the periphery of the fuel tank. These pickups are intended to close when no fuel is present, and then reopen when fuel returns. These pickups can be placed in series, parallel, or a combination so as to increase the likelihood that at least one pickup will be submerged in fuel. If two or more pickups are simultaneously above the fuel level, or if the fuel moves in the tank rapidly enough to uncover the pickups in quick succession so that one pickup closes before the previous one opens as can happen when a vehicle is operating at extreme attitudes, then all the pickups may close and not reopen when the fuel recovers them. This can occur even with as much as 30% of the total fuel capacity of the fuel tank still present and can lead to unexpected engine shut off, and, in some cases, the inability to restart the engine even after additional fuel is added to the fuel tank. This is due to the inability of the fuel pickups to open against the vacuum created by the fuel pump intake when the intake flow is sufficiently reduced or shut off.
Fuel systems of vehicles operating at extreme attitudes need to be more reliable. Fuel systems need to provide the ability to empty the fuel tank at normal and extreme attitudes. Fuel systems also need to provide even fuel delivery for consistent vehicle performance.